Another girl at the same hospital was seen wailing in pain after being wounded in an airstrike. Her name and age are unknown, as no family members accompanied her. Doctors believe they were killed in the same attack.

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Cluster bombs are explosives that project smaller "bomblets" that often lie around long after conflicts end and are difficult to clear. More than 100 countries have signed a treaty to ban their use.

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Now there are only five hospitals left in the area, and they're swamped with casualties.

The rules of war are not being abided by, a doctor at the hospital told ITV, adding that it was not just the innocent being struck, but the places that care for the sick and wounded.

At least seven people died and more remain trapped under rubble after "bunker-buster" bombs destroyed the M10 hospital in eastern Aleppo on Monday, opposition activists from the Aleppo Media Center said.

Photos:Heartbreaking images following Aleppo airstrike

A Syrian family leaves the area following a reported airstrike on Friday, September 23, in rebel-held east Aleppo. Following the airstrike, recovery teams from Syria Civil Defense, known as the White Helmets, began working to free the trapped and recover the dead, including small children.

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Photos:Heartbreaking images following Aleppo airstrike

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Photos:Heartbreaking images following Aleppo airstrike

This photo was released by the volunteer group Syria Civil Defense of the bodies of a man, with his knee pulled up near his face, and a child covered in dust after they were killed in the airstrike.

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Photos:Heartbreaking images following Aleppo airstrike

The volunteers work to recover the bodies the man and child.

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Photos:Heartbreaking images following Aleppo airstrike

A Syrian man carries the body of his nephew, recovered from the rubble.

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Photos:Heartbreaking images following Aleppo airstrike

The volunteers remove an infant's body from the destroyed building.

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Photos:Heartbreaking images following Aleppo airstrike

A Syrian woman carries the body of her infant after he was recovered.

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Monday's attack marked the third time in a week the M10 hospital was bombed. Airstrikes also pummeled the hospital last Wednesday and Saturday.

The facility, run by the Syrian American Medical Society (SAMS), was established in 2013 and was moved underground in 2014 after multiple attacks on the facility, the organization said.

It claimed the hospital was destroyed and that the five facilities left in the area now have to care for a population of 300,000 civilians, including more than 85,000 children.

The Syrian regime has tried to take control of eastern Aleppo since rebels took the area in 2012. In July, regime forces encircled the area, essentially cutting it off from food and medical supplies, sparking a humanitarian crisis there.